1. Field of the Invention
The present invention relates to intravascular catheter systems for monitoring physiological phenomena, for example, blood pressure in various regions of the heart, and in particular the present invention relates to an apparatus for effecting continuous flushing of such intravascular catheter systems.
2. The Prior Art
Catheter cannulation of an artery or a vein for pressure monitoring has long been recognized as an important technique for monitoring conditions in the thoracic cavity both during and after surgery. Such monitoring systems can provide valuable information pertaining to heart rate, stroke volume, cardiac output, duration of systole, and systolic, diastolic and mean blood pressures.
However, in order to insure a high quality clinical recording of central arterial pulse waveforms, it has been found necessary to continuously flush the catheter to prevent occlusion of the catheter end by clotting blood. In many instances such monitoring systems may be required to operate continuously over a period of several days, and it is thus essential to prevent occlusion of the catheter end by clotted blood.
Various types of continuous catheter flushing systems have theretofore been developed. An example of one type of system is illustrated and described in U.S. Pat. No. 3,581,733. In this type of system, a saline flushing solution is conducted through a long capillary tube which limits the amount of flushing solution passed through the catheter system to a predetermined small amount. A larger by-pass tube is also provided which may be used to quickly prime the system with the saline solution. A stopcock is provided with this tubing system so as to direct the flushing solution through either the large by-pass tube or through the long, narrow capillary tube.
One disadvantage of this type of system is that it is complicated to set up, requiring several connections to stopcocks and tubing. Moreover, the use of stopcocks in the system results in a decrease of the pressure pulse fidelity because of minute leaks in the stopcocks.
More recently, continuous catheter flushing devices have been devised which eliminate the complicated tubing and use of stopcocks described above. One such device is illustrated in U.S. Pat. No. 3,675,891. Another prior art device consists of a small unitary piece of apparatus which may be connected directly into the tubing of the catheter system. This type of device is sufficiently light in its weight that it may be suspended by the tubing. An example of one such type of prior art device is illustrated in FIG. 5 below.
However, even with the improved continuous catheter flushing device illustrated in FIG. 5, inaccuracies in the recorded pressure pulses have persisted. One reason for these inaccuracies is that the extremely sensitive pressure monitoring equipment will sense and will reflect any damping of the pressure pulses caused by the continuous catheter flushing apparatus.
Accordingly, what is needed is an improved continuous catheter flushing apparatus which incorporates the advantages of small size and efficient operation but which also maximizes the fidelity of the recorded pressure pulses by minimizing the damping effects otherwise created by the continuous catheter flushing device. Such an invention is disclosed and claimed herein.